International Head of Watches John Reardon pays homage to five generations of a horological legend, with examples from our Rare Watches sale in New York in December 2016

When watch collectors think of Patek Philippe, they generally think of the round perpetual calendar chronograph wristwatch. This combination of complications has grown to define Patek Philippe as a brand, and the watches under this umbrella are at the heart of horological legend. These timepieces have become icons of watch-investing and are now widely considered to be wearable works of art — the ‘holy grail’ for any collector of wristwatches.

Since launch in 1941, there have been five major evolutions, or generations, of the Patek Philippe perpetual chronograph. What follows is an explanation of the major differences in each style of this closely related multi-generational family, and the basic variants between Patek Philippe’s signature timepieces of the last 75 years.

Production numbers: Approximately 281Made in: Yellow gold, pink gold, and very few in steelCalibre: ValjouxDiameter: 35 mm

It all began at the Basel Show in 1941 when the original patriarch of the family was revealed to the world. As the first perpetual chronograph to be made in series by any maker, the watch quickly attracted the attention of royalty and the privileged, including King Farouk of Egypt, the King of Jordan, and of course Henry Graves, Jr., arguably the greatest watch collector of the 20thcentury.

The 1518 was a design first, setting the template for all of its descendants with its basic layout — apertures at 12, two subsidiary dials at 9 and 3, and a moonphase at 6.

Production numbers: Approximately 349 examplesMade in: Yellow, white and pink gold, and two examples in platinumCalibre: ValjouxDiameter: 36.2mm / 37.7mm

Widely acknowledged as one of the world's greatest-ever watch models, the 2499 has exerted a strong influence on the designs of many of the most renowned watchmakers. Over a period of 35 years, the 2499 was made in four separate series in a total production of only 349 pieces, the majority cased in yellow gold. The rarity of this model becomes evident when considering that an average of only nine watches left Patek Philippe's workshops annually.

The tell-tale ridged lugs instantly differentiate this watch from its predecessor and the larger diameter of this timepiece makes it attractively wearable. A 2499 is considered the ultimate statement watch today, instantly recognisable and coveted by collectors of modern and vintage alike.

Reference 2499 is generally divided into the following four distinct series:

The third iteration of the celebrated perpetual chronograph line of timepieces by Patek Philippe, the 3970 is the heir to the 2499, with which it shares the unmistakable case construction characterised by its sculpted lugs. It is, however, a bit smaller than its immediate predecessor. Also, the 3970 replaces the Valjoux calibre of its predecessors with a Lemania calibre.

The dial of the reference 3970 acquires two new indications: the 24-hour indication and the leap-year indication. Rather than encumbering the dial design, these additions are ingeniously placed inside the subsidiary dials at 6 and 9, thus keeping the overall look and feel of the dial very similar to that of reference 2499.

Beyond being aesthetically pleasing, the new indicators are extremely practical: the 24-hour indication allows the wearer to avoid setting the calendar when the time is around midnight and the calendar gear train is working, which would damage the movement. The leap-year indicator is invaluable when setting the perpetual calendar. Another practical addition is the push-piece for setting the month — previously one could only proceed one day at a time.

The 3970 represents the first ‘production era’ perpetual chronograph from Patek Philippe, and the fact that significant numbers of this reference were made relative to the 1518 and 2499 makes the 3970 more accessible in terms of price point. In fact, in the current market amazing examples of this reference can still be purchased for well under $100,000.

Considered one of the most perfect watches ever made by Patek Philippe in terms of design, the 5970 also had the shortest run of the family, having been in production for only six years.

Equipped with a movement based on a Lemania ébauche, it is heavily modified and finished by Patek Philippe. Is is also the last perpetual calendar chronograph of the company featuring the Geneva seal on the movement — Patek Philippe began stamping its movements with the Patek Philippe seal from Spring 2009 as a new quality benchmark for its mechanical timepieces.

When released in 2004 the model immediately enjoyed enormous popularity among collectors and was available in white gold or pink gold only until 2007, when production of these two versions ceased. Reference 5970 in yellow gold was in production only in 2008 and remains the rarest of the four colours. From 2008 until the end of production, the model was available exclusively in platinum.

Reference 5270 was introduced to the market at the Baselworld watch fair in April 2011, replacing the celebrated reference 5970. The white gold version was launched in 2011, and was followed by the pink gold version in 2015.

The watch houses the latest 29 535 PS in-house calibre with Patek Philippe's new hallmark of excellence, the PP Seal. It also features an additional day/night indication on the dial, as well as a separate leap-year cycle. Constant seconds and 30-minute registers are each on their own subsidiary dial, and two small apertures on either side of the date/moon phase subsidiary indicate the leap year and night and day.

The 5270, the youngest member of the family, is ’the son’ in this long and distinguished line of perpetual calendar chronographs. Not yet fully appreciated and generally undervalued, it is quietly undergoing dial changes year to year that attract the attention only of the most critical collectors’ eyes. But could this young five-year-old mature to be the collector’s item of the future? Only time will tell, but if the past really does inform the present, this is a good watch to buy at the right price today.

Incredibly, after a 75-year ongoing production run, all the perpetual chronographs in the Patek Philippe line carry very similar characteristics. Setting aside the mechanical and aesthetic evolutions between generations, the same DNA exists between the earliest 1518s made in the 1940s and the 5270s of today.

This article omits many close relatives of the round Patek Philippe perpetual chronograph, including the cushion-shaped 5020 ‘TV-set’ and the split-seconds 5004. Also, numerous variants are not included here: diamond and jewelled versions, caseback variants, bracelet versions, and countless dial variants.

On a final note, dials have become a defining characteristic in determining the value of many perpetual calendar chronographs. In particular, modern references with special-order dials — often called ‘unique’ dials — have been surfacing in recent times, and they continue to excite the market.

With such a wide variety of choice, one must consider the fact that owning a Patek Philippe perpetual chronograph is a rite of passage for both newly-minted collectors and buyers who are attracted to owning the best. There are versions of this classic watch for a wide spectrum of budgets, from $50,000 to well over $5 million. Many can afford to own one of these superlative timepieces. The real question to ask, however, is whether you can afford not to own one.